The assumption that stationary hotspots underlie the Earth’s lithospheric plates has been

most important in the development of the theory of plate tectonics. According to the fixed

hotspot hypothesis seamount trails are formed by volcanism penetrating the lithospheric

plates whilst moving over ”hotspots”of upwelling mantle. In turn, the azimuths and age

progressions of seamount trails can be used to quantify plate motions with respect to an

independent reference frame of hotspots in the mantle. Also, assuming fixed hotspots, the

direction of characteristic remanent magnetization in the basalts acquired during cooling

should always be the same. Even if due to plate motion the products of the hotspot are

located far away from the position of the hotspot itself, paleomagnetic studies on the

basalts must always provide the position of the hotspot itself. Recently the question

arose, why a hotspot with its origin deep in the mantle would not get advected in the

convecting mantle of the Earth. - In this thesis a possible motion of the Kerguelen hotspot

in the southern Indian Ocean and of the Louisville hotspot in the Pacific has been studied.

The Kerguelen hotspot is active since approximately 117 Ma. Since then it formed

the Kerguelen Plateau and the Broken Ridge in the southern Indian Ocean as well as the

Ninetyeast Ridge, which is the hotspot track going north up to India, and the Ramajal

Traps in India. Drilling into basement rocks of Broken Ridge and the Kerguelen Plateau

was aim of the Ocean Drilling Program, Leg 183, from December 1998 to February 1999.

Eight sites have been drilled. In seven of the sites also the sediments have been recovered.

In this thesis, a possible motion of the Kerguelen hotspot has been studied by

determining its paleolatitudes. First, basalts from the Kerguelen Plateau have been

studied paleomagnetically to compare the paleolatitudes with the latitude of the hotspot

itself. Basement from a drillsite on the central Kerguelen Plateau (Site 1138) and of a

site on the northern Kerguelen Plateau (Site 1140) were suitable for a determination of

paleolatitudes. A sufficient number of independent lavaflows has been penetrated and

sampled there to properly average out paleosecular variation, an important requirement

for determining paleolatitudes. The characteristic magnetization from the subaerial Site

1138 with AA- and Pahoehoe lava and of the submarine Site 1140 with its pillow basalts

is carried by magnetite and titanomagnetites and -maghemites and consists of a single

remanence component with sometimes a small viscous overprint, that could easily be

removed during demagnetization. Stepwise demagnetization in an alternating field and

stepwise heating of the specimens provided the inclination value of the characteristic

magnetization very precisely with small error. Conversion of the mean-site inclination

into the paleolatitude of a site provided a latitude of λ = 43.6◦S (max.: 47.8◦S; min.:

37.9◦S) for Site 1138 on the central Kerguelen Plateau and a latitude of λ = 35.8◦S (max:

43.0◦S; min.: 28.9◦S) for Site 1140 on the northern Kerguelen Plateau. In Site 1136 on the southern Kerguelen Plateau only two lava flows have been sampled. Therefore

paleosecular variation could not be averaged out properly. Site 1142 on the Broken

Ridge has been tilted and deformed tectonically after its formation, as was found from

seismic explorations prior to drilling, and the inclination of the magnetization could

therefore not be used for a determination of paleolatitudes. Compared to the latitude of

the Kerguelen hotspot at 49◦S, the paleolatitudes of the central and northern Kerguelen

Plateau are further north. This result agrees with previous paleomagnetic studies on the

southern Kerguelen Plateau and the Ninetyeast Ridge, where paleolatitudes have been

found that indicate also a formation north of the present-day hotspot position. This

difference indicates a southward movement of the hotspot since the Cretaceous relative

to the